WO2004007963A1

WO2004007963A1 - Volume screw machine of rotary type

Info

Publication number: WO2004007963A1
Application number: PCT/IB2003/003233
Authority: WO
Inventors: Alexander Gorban
Original assignee: Elthom Enterprises Limited
Priority date: 2002-07-17
Filing date: 2003-07-14
Publication date: 2004-01-22
Also published as: KR20050056935A; IL166224A; RU2336437C2; ATE318374T1; WO2004007964A1; AU2003281080A1; DE60209324D1; AU2003247068A1; IL166223A; US20060127259A1; WO2004007962A1; AU2003250438A1; AU2003247102A1; RU2005104239A; UA83632C2; CN100473834C; RU2005104242A; WO2004007965A1; MXPA05000634A; US7540728B2

Abstract

A rotary screw machine comprising both an enclosing (1, 2, 4, 5) and an enclosed screw element (2, 3, 5, 6) having respective profiled inner (101, 102, 104, 105) and outer surfaces (202, 203, 205, 206) is constructed in such a manner that the profile of the outer surface of the enclosed element is inscribed into a ring of radial extent 2a with average radius ROm with a symmetry order of nm, and that the profile of the inner surface ot the enclosing element is inscribed into a ring of radial extent 2a with average radius Rom+E with a symmetry order of nf, nF>nM, in particular nF=nM+1. One of the elements is centred about a first axis O, and the other one of the elements is centred about a second axis O’ parallel to the axis O with eccentricity E. The other element is rotatable about its axis O’, and this axis O’ is also rotatable about the first axis. Preferably, 2a=2e. A statically and dynamically balanced machine is obtained.

Description

VOLUME SCREW MACHINE OF ROTARY TYPE

FIELD OF THE INVENTION

The invention relates to a volume screw machine of rotary type (rotary screw machine).

DESCRIPTION OF THE PRIOR ART

Volume screw machines of rotary type comprise conjugated screw elements, namely an enclosing (female) screw element and an enclosed (male) screw element. The enclosing screw element has a profiled inner surface (inner screw surface), and the enclosed screw element has a profiled outer surface (outer screw surface). The profiled surfaces (screw surfaces) are non-cylindrical and limit the elements radially. They are centred about respective axes which are parallel and which usually do not coincide, but are spaced apart by a length E (eccentricity).

A rotary screw machine of three-dimensional type of that kind is known from US 5,439,359, wherein an enclosed element engaged into an enclosing element is in planetary motion relative to the enclosing element.

A first component of this planetary motion drives the axis of the profiled outer surface of the enclosed element to make this axis describe a cylinder of revolution having a radius E about the axis of the profiled inner surface of the enclosing element, which corresponds to an orbital revolution motion. That is, the axis of the enclosed element rotates about the axis of the enclosing element, wherein the latter axis is the principal axis of the machine.

A second component of this planetary motion drives the male element to make it rotate about the axis of its screw surface. This second component (peripheral rotation) can also be called swivelling motion.

Instead of providing a planetary motion, a differential motion can be provided. Usually, synchronizing coupling links are used therefor. However, the machines can also be self-synchronized by using suitable screw surfaces. Rotary screw machines of the kind described above are known for transforming energy of a working substance (medium), gas or liquid, by expanding, displacing, and compressing the working medium into mechanical energy for engines or vice versa for compressors, pumps, etc. They are in particular used in downhole motors in petroleum, gas or geothermal drilling. In most cases, the screw surface have cycloidal (trochoidal) shapes as it is for example known from French patent FR-A-997957 and US 3,975,120. The transformation of a motion as used in motors has been described by V. Tiraspolskyi, "Hydraulical Downhole Motors in Drilling", the course of drilling, p.258-259, published by Edition TECHNIP, Paris. Rotary screw machines of the prior art have rated profiles of the end sections of elements in the planes which are normal to the longitudinal principal axes of the elements, and which are characterized by the pitches (periods) P_m and P_f, respectively, of a screw turn of the end sections about central axes. When P_m and P_f have finite values, as a result of mechanical curvilinear contact between the inner surfaces of enclosing elements and the outer surfaces of enclosed elements, the closed chambers are formed, and they are executing an axial motion at a relative motion of the conjugated surfaces in space, and thereby a working medium of a machine is transported from one end of the conjugated screw elements to the other end thereof.

In some of the machines of the prior art, the profiled surfaces of the enclosing and enclosed elements are inscribed into rings. In one embodiment, the directrix of a profiled outer surface of an enclosed element has a symmetry order n_m about a central axis O, and the profile is inscribed into a ring having an average radius R°_m. The directrix of an inner surface of an enclosing element has a symmetry order of

about a central axis O thereof, and its profile is inscribed into a ring having an average radius of R°_f=R°m+A and having a radial extent of 2a. The average radius R°m may be considered as the profile parameter, and A as the form parameter.

Other geometries of the profiles are for example known from US 5,439,359 and US 3,168,049.

The known rotary screw machine with conjugated elements of curvilinear form (form of trochoids, hypertrochoids, etc.) have limited technical potentialities because of imperfect conjugation (also in theory) of those profiles along the dividing line of the working chambers and availability in those machines of special means for starting a rotor interplanetary motion about a stator axis with eccentricity E. These forms of profiles of screw pairs complicate the technology for their production, give rise to increase wear in the places of reciprocating contact, as well as to breaking machine tightness in axial direction between high and low pressure regions of a working medium and appearance of leakage of a machine working medium in pairing volume efficiency (as well as the general efficiency) of the machine. That results in restriction of the working medium volumes with subsequent constriction which is not always permissible. The centrifugal forces of inertia of planetarily moving rotors of the machines known in the prior art fail to balance on the parts and these forces load the machine bearings. By that, their technical potentialities as regards the range of the rotary velocities and the weight-dimension parameters, and the machine construction is complicated because of the need for installing the means for their static and dynamic balancing.

SUMMARY OF THE INVENTION

It is an object of the invention to expand the technical and functional potentialities of the rotary screw machines of the prior art, to eliminate leakages and constriction of a working medium, to eliminate any special means for driving the elements executing the planetary motion (the satellites) about the principal axis of the machine, and to dispense of any means for balancing.

According to the invention, a rotary screw machine is provided which comprises an enclosing screw element having a profiled inner surface and an enclosed screw element having a profiled outer surface. The profile of the outer surface of the enclosed element is inscribed into a ring of radial extent 2a with average radius R°_m, wherein the profile of the outer surface has a symmetry order n_m. The profile of the inner surface of the enclosing element is inscribed into a ring of radial extent 2a with average radius R°_m+E. One of the elements is centred about a first axis O, and the other one of the elements is centred about a second axis O' parallel to the axis O having eccentricity E. The other (second) element is rotatable about its axis O', and the second axis O' is rotatable about the first axis O. In other words, the second element (preferably the enclosed element) performs a planetary motion, i.e. there is a revolution of its axis provided, and swivelling is also provided.

By choosing the eccentricity E to have a value which is equal to the difference of the average radii of the two elements, the two screw elements are put into perfect contact, and a perfect motion of one element with regard to the other element is obtained, thereby improving the formation of the working chambers and the transport of the medium in the machine.

According to a preferred embodiment of the invention, the profiles of both the inner surface of the enclosing screw element and the outer surface of the enclosed screw element are inscribed into rings of radial extent 2a=2E. By that measure, a still more perfectly working machine is obtained because the value of the eccentricity E is here used for the value of a third parameter playing a role in the machine. Preferably, the symmetry order of the profile of the enclosing element, n_f is one symmetry order higher than that of the profile of the enclosed element, n_m, i.e. n_f=n_m+l.

In order to obtain a still more perfectly working rotary screw machine, the average radii R°_m of the ring in which the profile of the outer surface of the enclosed screw element is inscribed can be chosen equal to the value of eccentricity E times the symmetry order n_m of the profile of the outer surface, R°_m=n_m E (possibly with a constant factor), and the average radius R°m+E of the ring in which the profile of the inner surface of the enclosing screw element is inscribed is equal to the value of eccentricity times the symmetry order n_f of the profile of the inner surface, that is R°_m+E=(n_m+l)E=n_fE.

The rotary screw machine of the present invention is not limited to comprising only two elements, a single enclosing and a single enclosed element. Rather, a plurality of screw elements can be provided which have both an outer and an inner profiled surface (with identical symmetry order both), and which are placed in between of an outer enclosing screw element (generally having only an inner profiled surface) and an inner enclosed screw element (generally having only an outer profiled surface). These screw elements can then be placed one in the interior of a respective outer one, i.e. one in the interior of each other. The symmetry order of the profiles of the surfaces of the screw elements can increase starting from that of the inner enclosed screw element, n_m. In particular, it can be increased by 1 to the next enclosing screw element, thereby obtaining a set of screw elements in which the inner enclosed screw element has a profile of symmetry order n_m, the next enclosed screw element has a profile of symmetry order n_m+l, the next screw element has a symmetry order of n_m+2, etc., wherein finally the symmetry order of the profile of the inner surface of the outer enclosing screw element is n_m+k-l, wherein k is the total number of screw elements.

The average radii of the rings into which the respective profiles can be inscribed can once again be multiples of E, possibly of a constant times E, wherein the factor is the symmetry order of the respective screw element.

The most simple version of such an advanced rotary screw machine is a rotary screw machine with three elements, i.e. with an outer enclosing screw element, an inner enclosed screw element and a middle (intermediate) screw element which is both enclosed and enclosing.

If a plurality of these elements is provided, they can be arranged in such a manner that rotatable elements i are each rotatable about a respective axis Oj having eccentricity Ei, and that the axes Oi are chosen in such a manner as to obtain a (statically and) dynamically balanced machine. This choice takes the mass centres into consideration. In particular, the mass centres of the single elements are placed in such a manner about the principle axis O that the elements which are not centred about the principal axis, when taken altogether, have their mass centre placed in the principal axis. (The mass centre is the centre of gravity of a slice of the screw elements, i.e. it corresponds to the axes provided through the centre of gravity of the whole screw element.)

As explained in more detail below, a preferred profile of the end sections of the screw elements can be obtained by defining hypocycloids with radius Ro in the form of the parametric equations dependent on parameter t:

R_y=RoSin t and

Rx=nmE+RoCos t, and by enveloping these hypocycloids by rolling a circle such that an envelope D_m is obtained which can be defined by using the parametric equations based on parameter t: x(t)=E cos[(n/(n+l))[arcsin(sin t)-t]]+n cos[(arcsin(sin t)-t)/(n+l)]) +r₀(z)cos[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; y(t)=E(sin[(n/(n+l))[arcsin(sin t)-t]]+n sin[(arcsin(sin t)-t)/(n+l)]) +r₀(z)sin[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; wherein n=n_m,_rl (n_m,_f ist he symmetry order of the respective element). The function r₀(z) is monotonaly varying.

As mentioned above, the rotary screw machine according to a preferred embodiment of the invention comprises a first set of elements having profiles with ascending symmetry order. Instead of providing further elements having ascending symmetry order, a second set of elements can be provided which comprises the same number of elements and in which the symmetry orders of the elements of the first set are repeated, i.e. when the elements are given ordinal numbers, elements of the first and second sets having the same ordinal numbers have profiles having the same symmetry order. The second set can then be placed into a cavity of the first set. Of course, not only a single further (second) set can be provided. Rather, a plurality of additional sets of elements can be provided, one being placed in the interior of another, wherein in each set the same symmetry order features (sequence of symmetry orders of the profiles of the single (corresponding) elements) are present. Preferably, screw elements of different sets of screw elements with profiles having the same symmetry order which are rotatable are placed in the machine in such a manner that the eccentricity of the axes about which they are rotatable is well-defined, namely such as to obtain a balanced machine. In other words, once again, the eccentricity can be chosen in such a manner as to place the mass centre of the rotatable elements when taken together into the principal axis of the machine, thereby obtaining a (statically and) dynamically stable machine.

If each set comprises three elements, it is preferably the middle (intermediate) element (the element which is both enclosing and enclosed) which can be rotatable about an axis which has an eccentricity which is defined in such a manner as to fit to the eccentricity of the other middle (intermediate) elements.

According to a first preferred embodiment of the invention, corresponding ones of the screw elements (i.e. screw elements having profiles with the same symmetry order) in each set are driven into rotation (are rotors), and these driven elements (rotors) are mechanically coupled (to a drive shaft, for example).

Furthermore, non-driven elements can also be mechanically coupled to each other. For example, a crank-like mechanism can be provided for the non-driven elements.

The rotors (directly driven elements) are preferably the inner elements of each set, i.e. are preferably only enclosed and not enclosing. In one embodiment, the outer elements of each set are not rotatable (are stators), i.e. a planetary mechanism is thereby obtained. In a second embodiment, the outer elements are counter-rotated (for example by coupling them to the rotors via an inverting mechanism), thereby obtaining a differential mechanism.

According to another aspect of the present invention, which is presently not claimed herein, a rotary screw machine comprises at least two sets of at least two conjugated screw elements (including at least one enclosing screw element and at least one enclosed screw element, wherein one set is placed in the interior (in a cavity) of another set). Corresponding ones of the screw elements (when numbered, for instance starting from the innermost screw element of each set) all have screw profiles (outer and/or inner) of the same symmetry order, e.g., when seen at the end sections of the screw elements. According to a preferred embodiment of that aspect, the symmetry order is increasing (preferably by 1) from the interior to the exterior of each set. According to a further preferred version, corresponding elements of the different sets substantially have the same shape, wherein only the dimensions of the elements differ. Once again, preferably each set comprises three different elements, an enclosing screw element, an enclosed screw element and an intermediate screw element which is both enclosed and enclosing and has both outer and inner profiled surfaces. In that embodiment, preferably the intermediate elements of each set are (mechanically) coupled to each other, for example by a crank mechanism. Moreover, the inner elements (the enclosed elements) of each set can also be (mechanically) coupled. For example, these inner elements can be rotors which rotate in synchronism or at least with angular velocities having proportionality. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will more easily be apparent from the following description of preferred embodiments thereof which is given with respect to the accompanying drawing, in which: Fig.l shows a scheme used for explaining the principle of forming the end profile of the screw surface of the elements used in the rotary screw machine according to the invention,

Fig.2 shows a three-dimensional representation of a curvilinear screw element having a symmetry order of n_m=5, Fig.3 shows a longitudinal section of a rotary screw machine according to a first preferred embodiment of the invention,

Fig.4 shows a cross section along the line IV-IV of fig.3, and

Fig.5 shows a longitudinal section of the rotary screw machine according to a second preferred embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE

INVENTION

A rotary screw machine according to the invention comprises a plurality of enclosing screw elements and of enclosed screw elements, wherein intermediate elements can be both enclosing and enclosed. The enclosing screw elements have a profiled inner surface, whereas the enclosed screw elements have a profiled outer surface.

In the present invention, the profiled surfaces have a particular shape D_m which is constructed in the following manner as explained with respect to fig.l in which the profile D_m has a symmetry order of n_m=5:

One starts with the construction of a hypocycloid I^" which has the parametric form (dependent on parameter t): x(t)=E cos(n_m-l)t-rE(n_m-l)cos t y(t)=E sin(n_m-l)t-E(nm-l)sin t. Such hypocycloids r of a symmetry order n_m, (n_m+l), (n_m+2),

... (n_m-ri) are the curve which is described by a point A of a circle having the radius O_A=E and the centre O_E and which rolls (without sliding) along the inner surface of another circle with radii equal to En_m, E(n_m+1), E(n_m+2), ... E(n_m+i) having a centre O_m as it is shown in fig.l. The points where the point A contacts these circles are indicated at B, C, D, F, I. An equivalent way of constructing such a hypocycloid r of a symmetry order n_m, (nm+1), (n_m+2), ... (n_m+i) is based on describing the curve the point A of circles with radii E (n_m-l), E(n_m+1), ... E(n_m+l+i) and centre O₂ which roll (without sliding) along the inner surface of circles having radii equal to En_m, E(n_m+1), E(n_m+2), ... E(n_m+2+i). The profile D_m used for the screw elements in the present invention is, starting from the hypocycloid T, obtained by rolling a circle with radius r₀ which is for example equal to 2E, r₀=FR=2E in fig.l, along the hypocycloid l^~, wherein during the rolling, the centre of that circle moves along the hypocycloid. If ro is chosen to vary monotolly along the z-axis (the axis perpendicular to the plane of the drawing in fig.l), one obtains for the profile D_m the parametric equations (dependent on parameter t): x(t)=E cos[(n/(n+l))[arcsin(sin t)-t]]+n cos[(arcsin(sin t)-t)/(n+l)) +r₀(z)cos[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; y(t)=E(sin[(n/(n+l))[arcsin(sin t)-t]]+n sin[(arcsin(sin t)-t)/(n+l)]) +r₀(z)sin[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; wherein n=n_m-l or n=nrl.

Fig.2 shows a three-dimensional representation of a screw element obtained by using the construction described above. It is to be noted that all screw elements which have both a profiled inner surface and a profiled outer surface, i.e. which are both enclosing and enclosed, necessarily have a non-zero wall 5 thickness. That is, the inner profile 105 is necessarily a little bit smaller than what one would obtain according to the construction described with respect to fig.l, and the outer profile 205 is necessarily a little bit bigger than the theoretically constructed profile. One can construct the screw element in such a manner that the profile constructed as described above is obtained in exactly the middle of the wall 5, i.e. that half the thickness of the wall 5 is present in the interior of the profile and half that thickness is present in the exterior. However, one can place the theoretical profile D_m also a little bit closer to the interior of the wall 5 than to the exterior. For example, one could divide a wall thickness d into two portions, namely of thickness d(n_m-l/2n_m) and d(n_m+l/2n_m), wherein n_m is the order of symmetry of the respective element, and wherein n_m-l is the order of symmetry of the element enclosed by that element, and wherein n_m+l is the symmetry of the element enclosing the respective element. The profile D_m is constructed in such a manner that the inner conjugation (engagement) of an enclosing profile D_f (constructed analogously) which is specially centred in O_f having a radius (n_m+l)E with the enclosed profile D_m which is specially centred in O_m and has a radius N_mE provides for n_m+l contact points and completely satisfies a theory of internal conjugation. All the normals of the tangent lines in the contact points of the profiles meet on a line of the centres (off the centres Of, O_m) in a pole of engagement.

In the preferred embodiments, the conjugated elements are combined in different sets, namely in two different sets each having the form of a kinematic mechanism formed by conjugated elements and links of synchronization. One set is placed in the interior of another one, i.e. one has a succession of different sets one in cavities of a respective outer one. These cavities do in the preferred embodiment not have any profiled surfaces such that the different kinematic mechanisms are separated. In each set, the symmetry orders of the profiles of the end sections of any of the elements, beginning from the inner (enclosed) element which has a symmetry order of n_m is increasing such that the director curves have a symmetry order of n_m, (n +l), (n_m+2), ... (n_m+i), ... about their axes, said director curves being constructed in the manner described above with respect to fig.l.

Corresponding screw elements in the different sets, i.e. those elements which have the same ordinal number when counted beginning with the inner element, can have the same symmetry order. In particular, they can even be made geometrically similar, wherein the dimensions of the elements in the inner set are smaller than those of the elements in the outer set.

Fig.3 shows a first embodiment of the rotary screw machine of the present invention which comprises a body 9, an inner set of conjugated elements 1, 2 and 3 and an outer set of conjugated elements 4, 5 and 6 with screw surfaces the axes of which are parallel.

A machine comprising the two sets of screw elements: set 1: first female element 1 (profile 101), centred about fixed axis (O); second element 2 (profile 202), executing planetary motion, centred about second own axis (O₂); third element 3 (profile 203), centred about fixed axis (O); working chambers of set 1-300,400; set 2: first element 4 (profile 104), centred about axis (O); second element 5 (profile 205), executing planetary motion, centred about second axis (O₅); third element 6 (profile 206), centred about fixed axis (O). Working chambers of set 2-500,600; elements 2,5 to swivel about axes passing through centre O2, O₅, respectively.

In both sets, the outer element 1 and 4, respectively, is a stator. It is part of the invention that these stators 1 and 4 are mechanically connected. Furthermore, the inner elements of each set are rotors 3 and 6. Once again, according to the present invention, the rotors 1 and 4 are mechanically connected such that they turn about the principal axis Z of the rotary machine with the same angular velocity. The intermediate elements 2 and 5 which are both enclosing and enclosed are two-sided rotor-satellites. They can execute a planetary motion without any additional means to start them into that planetary rotation. Fig.4 shows a cross section taken at the lines IV-IV in fig.3. As one can see in that figure, the rotors 3 and 6 have a symmetry order of n_m=4, the rotors-satellites 2 and 5 have a symmetry order of ni=n_m+l=5, and the stators have a symmetry order of n_f=n_m+2=6. The profiles of the elements, namely the inner surfaces 101, 102, 104 and 105 and the outer surfaces 202, 203, 205 and 206 are constructed in the manner described above with respect to fig.l.

Both the rotors 3 and 6 and the stators 1 and 4 are centred about the principal axis Z. The planetary rotor-satellite 2 is centred about a centre O₂ having eccentricity Ei, and the centre O₅ of the planetary rotor-satellite 5 is placed as to have an eccentricity E₂. The centres O₂ and O5 are set at diametrically opposite points of the axis. Due to the synchronized motion, the line formed by the centres O₂, the axis Z and O₅ moves, and the centres O₂ and O₅ always remain at the diametrically opposite points. Thereby, the whole system is statically and dynamically balanced. The eccentricities Ei and E₂ are chosen in such a manner as to balance the masses of the planetary rotor-satellite elements 2 and 5.

As shown in fig.3, a working medium of the machine (liquid or gas) is supplied to the open left end surface of the elements 1 to 6 and is removed from the right open end surface of the elements 1 to 6 (see arrows). The body 7 which is connected to the stator 1 can be mechanically rigidly connected to the stationary body 9 of the machine, and a shaft 8 mechanically connected to the rotors 3 and 6 can serve as an output shaft. The shaft 8 can also be connected mechanically to the stationary body 9. In that case, the body 7 can serve as an output shaft, i.e. can be used as a motor-wheel.

The machine shown in fig.3 operates as follows: It has one independent degree of freedom of the rotary motion of the shaft 8 or the body 7. In each set, rotation of first screw elements 1 or 3 about central axis may be carried out (or element 1 or 3 may be stationary) and planetary motion (including circular progressive motion) of the male (second) screw element 2 or 5 conjugated with the first one may be carried with the help of the third (male) conjugated screw element 3 and 6 which is coaxial to the first one. In general case, all of the elements of set the three mechanical degrees of differential motion (rotation of the first element 1,4 rotation of the element 3,6, a revolution of an axis of the second element 2,5 of one set about the fixed central axis, swivelling of the second element 2,5 two of which may be chosen independently. If one of the elements of set 1,2,3 and 4,5,6 is fixed then the set has the two mechanical degrees of planetary or birotative motion one of which may be chosen independently. Jointly, all the conjugated elements 1 to 6 restrict the working chambers of the machine and cause them (with the motion of the conjugation contacts of the elements) to move along the axis Z.

The angular cycle Tι pair of female-male conjugated elements is given by equation: Tj=2π/[n_m|(ωf/ωi)-(ω_m/ω_i)|] where: ω_f,ω_m-own angular velocity of female and male elements about own centres; ωr angular velocity of independent element, turn angle of which defines the value of T; n_m-symmetry order outer envelope male element of pair of female-male conjugated elements. With fixed element 1,4 planetary motion of element 2,5 (profile

202,205) and rotation element 3,6 is defined by the following parameters:

nι,4=6;

n3,6=4; ω_re(₂,5)= ω_r0(3,6)/(l- (nι,4/n₃,6))=-l/(l-6/4)=2; ω_m(2,5)= ω_S(₂,5)=ωre(2,6)(l-nι,4/n₂,₅)=2(l-6/5)=- 0.4; T₈ (3oo,5oo)=2π/5(0+0.4)=π=180 degrees turn angle of shaft 8; Ts (4oo,6oo)=2π/4(-0.4+l)=π/l,2=150 degrees turn angle of shaft 8; With fixed element 3,6 planetary motion of element 2,5 (profile 202,205) and rotation element 1,4 is defined by the following parameters: ω_m(3,6)=0;

n₂,₅=5; n3,6=4;

ω_r0(3,6)/( l-i n 1,4) =1/(1- 4/6)=3; ω_m(2,₅₎=ω_S(25)=ω_re₍₂,₅₎(l-n₃,₆/n₂,₅)=3(l-4/5)=0.6;

T₇₍₃oo,₅oo₎=2π/5(l-0.6)=π=180 degrees turn angle of body 7; T₇(₄oo,₈oo)=2π/4(0.6-0)=π/l,2=150 degrees turn angle of body 7.

A complete cycle of an axial movement of the working chambers 300, 500 between the elements 1, 2 and 4, 5 by a period in the machine shown in fig.3 (symmetry orders and scheme of kinematic interaction given as described above) occurs, when the output shaft 8 or the body 7 rotate about an angle of 180 degrees. In other words, there are two complete cycles during one rotation.

A complete cycle of an axial movement of the working chambers 400, 600 between the elements 2, 3 and 5, 6 in the machine shown in fig. 3 (symmetry orders of its elements and scheme of their kinematic interaction given as described above) occurs, when the output shaft 8 or the body 7 rotate about 150 degrees. In other words, there are two and a half cycles during one rotation.

The interconnected rotary motions about the principal axis Z of the machine and about the own axes of the elements occur with three degrees of freedom of the mechanical rotation. If one takes the relative angular velocity of the inner rotors (enclosed elements) 3 and 6 as to be -1 with respect to the stationary stators (enclosing elements) 1 and 4, the relative angular velocity ω_re(₂, ₅) of the line found by the centres O₂-O-O₅ of the rotor-satellites 2 and 5 about the axis Z can be determined by the formula ω_re (₂,

3)/2=+2 (n_m(6, 3)=4 is the symmetry order of the elements 6 and 3). The relative angular velocity ω_s (_{2 5}) of the rotor- satellites 2 and 5 about their centres O₂ and O₅, respectively, is given by ω_S(_{2 5})=(ω_re-4)/5=-0.4.

One can also define the relative angular velocity of the movable status 1 and 4 as +1 with regard to the stationary central rotors 3 and 6 and then obtain ω_re(2,

4)/2=3 (n_m(ι,

3)+2=6), and ω_S(₂,

Fig. 5 shows a second preferred embodiment of the rotary screw machine according to the invention. Once again, there are two sets of screw elements provided, a first set 1', 2', 3' and a second set 4', 5' and 6'. (In fig. 5, elements which correspond to the elements of the machine shown in fig.3 are given the same numbers, but with an additional stroke.) Once again, the elements 3' and 6' are rotors, and the elements 2' and 5' are planetary rotor-satellites which are two-sided, i.e. which are both enclosing and enclosed screw elements. Furthermore, the cross-section shown in fig.4 is also this cross section of the machine shown in fig.5. In other words, the shape of the screws has not been changed. What has been changed is that they are no longer any stators (non-rotating elements). Rather, the elements 1' and 4' are also rotors rotating the other way round than the rotors 3' and 6', the latter rotors therefore being counter-rotors. Once again, the counter-rotors 3' and 6' are connected to each other and are rotated by the shaft 8'. The rotors 1' and 4' are also connected to each other. Furthermore, the rotative pairs of the elements 1', 4 on the one hand and 3', 6' on the other hand are mechanically connected by a matching unit in the form of the reducer, for example as shown in fig.5 in the form of an inverter 10 of the rotation direction which has a transmission ratio of [-1]. The inverter 10 mechanically connects the body 7 to the pair of rotors 3', 6' of the shaft 8' and inverts the rotation direction of the body 7 and transfers the inverted rotation to the shaft 8'.

In the machine shown in fig.5, the mechanically connected rotors 1', 4' and the mechanically connected counter-rotors 3', 6' therefore rotate simultaneously about the axis X in opposite directions having the same relative angular velocities ω_r0(i,4)=+l and ω_ro(3, 6)=-l, respectively.

Differential motion with planetary motion of elements 2,5 and rotation of elements 1,3 and 4,6 is defined by the following parameters:

4)=5; ωm(2,5)=ω_S(₂,5)=(ω_ro(i,4)-ωre(₂,5))nι,4/n₂,5+ωre(₂,5)=(l-5)(6/5)+5=0.2; Tι₍3oo,5θθ)=2π/5(l-0.2)=π/2=90 degrees; Tι₍₄oo,6oo)=2π/4(0.2+l)=π/2.4=75 degrees. From the above, it is evident that, in case of differential motion of elements, angular cycle twice decreases and accordingly the efficiency of method increases.

The direction of axial movement of working medium along axis Z in each set of chambers 300,400 and 500,600 is defined by the direction of revolution of centres O₂, O₅, therefore in order to choose the same directions of working medium movement, give the same directions of revolution of centres O₂, O₅, and in order to choose the opposite directions of working medium movement in chambers 300,400 and 500,600 give the opposite direction of revolution of centres O₂, O5.

The relative angular velocity ω_re(₂, 5) of the revolution of the line of the centres O₂-O-O₅ (shown in fig.4) of the rotors-satellites 2 and 5 about the axis X with respect to the velocity of the rotors 2' and 5' is then given by the expression

6)+3co_r0(i, 4)=5. The relative angular velocity ω_S(_{2, 5}> of the rotors-satellites 2', 5' about their axes O₂, O₅ with respect to a velocity of the rotors 1', 4' is given by ω_S(₂, 5)=0.8[ω_rO(3,

6)" i re(₂, 5)]+ ω_re(₂, 5)=+0.2. The differential movement of the screw machine shown in fig.5 has the effects that the cycles of an axial movement of the working chambers are performed at exactly half the values of shaft turn with regard to that of the screw machine shown in fig.3, due to the counter- rotation. Namely, one cycle of an axial movement of the six working chambers between the elements 1' and 2', 4' and 5' is made when the output shafts 7', 8' turn about an angle of 90 degrees. That is, there are four cycles during one rotation. The cycle of an actual movement of the five working chambers between the elements 2' and 3', 5' and 6' is given when the output shafts 7', 8' turn about 75 degrees. Per rotation of the shafts, there are five cycles.

The counter-rotative rotation of the output shafts of the machine makes it possible to join up to the machine effective counter- rotative executive devices such as counter-rotative screws (propellers) of air or water movers, counter-rotative cutting elements of saws, crushers, etc.

Generally, the rotative conjugated elements of the screw machine can be connected (by transfer mechanisms) to rotative elements of external mechanisms or devices. This mechanical connection can be used for example together with a counter-rotative turbine, a compressor or a counter-rotative electric machine, with counter-rotative screws of an air or water vehicle, with counter-rotative blades or saws, etc.

Both preferred embodiments described above with respect to fig.3 and 5 have in common that the volume of the rotary screw machine is very effectively used because two sets of conjugated elements are placed one in the interior of the other. The shapes of the profiled elements are well-defined such as to provide for a motion of the medium in the working chambers in an optimum manner. Mechanical connections have been chosen such as to obtain a statically and mechanically balanced machine.

Claims

1. A rotary screw machine, comprising:

- an enclosing screw element (1, 2, 4, 5) having a profiled inner surface (101, 102, 104, 105) and

- an enclosed screw element (2, 3, 5, 6) having a profiled outer surface (202, 203, 205, 206), wherein the profile of the outer surface of the enclosed element is inscribed into a ring of radial extent 2a with average radius R°_m, said profile of the outer surface having a symmetry order n_m,

- wherein the profile of the inner surface of the enclosing element is inscribed into a ring of radial extent 2a with average radius R°m-rE, said profile of the inner surface having a symmetry order n_f which is higher than the symmetry order n_m of the profile of the outer surface, and

- wherein one of the elements is centred about a first axis O, and wherein the other one of the elements is centred about a second axis O' parallel to the axis O with eccentricity E,

- said other one of the elements being rotatable about its second axis O', and said second axis O being rotatable about said first axis O'.

2. The rotary screw machine of claim 1, wherein said profiles are inscribed into rings of radial extent 2a=2E.

3. The rotary screw machine of claim 1 or 2, wherein the profile of the enclosing element (1, 2, 4, 5) has a symmetry order of n_f which is one symmetry order higher than that of the profile of the enclosed element (2, 3, 5, 6) of

4. The rotary screw machine of claim 3, wherein the average radius R°_m of the ring in which the profile of the outer surface into which the profile of the outer surface is inscribed is equal to the value of eccentricity E times the symmetry order n_m of the profile of the outer surface, R⁰ _m=n_m E, and wherein the average radius R°_m+E of the ring into which the profile of the inner surface is inscribed is equal to the value of eccentricity E times the symmetry order nf of the profile of the inner surface, R⁰ _m+E=(n_m+l) E=n_f E.

5. The rotary screw machine of claim 3 or 4, wherein said enclosing screw element (2, 5) further has a profiled outer surface (202, 205), said outer surface of the enclosing screw element having a symmetry order of n +l, and wherein a further enclosing screw element (1, 4) having a profiled inner surface (101, 104) is provided, said inner surface of the further enclosing screw element having a symmetry order of n_m+2.

6. The rotary screw machine of claim 5, comprising a plurality of screw elements (2, 5) each having an outer and an inner profiled surface (102, 202; 105, 205) with identical symmetry order, and an outer enclosing screw element (1, 4) and an inner enclosed screw element (3,

6), said screw elements placed one in the interior of another one, whereas the symmetry order of the profiles of the surfaces of the screw elements increases starting from that (n_m) of the inner enclosed screw element (3, 6) by 1 to the next enclosing screw element such that the symmetry order of the profile of the inner surface of the outer enclosing screw element is n_m+k-l, k being the total number of screw elements.

7. The rotary screw machine of claim 6, wherein the elements are arranged in such a manner that rotatable elements i are rotatable about an axis Oi having eccentricity Ei, wherein the axes Oi are chosen in such a manner as to obtain a statically and dynamically balanced machine.

8. The rotary screw machine of any of claims 3 to 7, wherein the profiles of the end sections of the screw elements having a symmetry order of n+1 have the curvilinear shape defined by the equations dependent on parameter t: x(t)=E cos[(n/(n+l))[arcsin(sin t)-t]]+n cos[(arcsin(sin t)-t)/(n+l)) +r₀(z)cos[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; y(t)=E(sin[(n/(n+l))[arcsin(sin t)-t]]+n sin[(arcsin(sin t)-t)/(n+l)]) +r₀(z)sin[arcsin(sin t)-(arcsin(sin t)-t)/(n+l)]; wherein r₀(z) is monotonally varying.

9. The rotary screw machine of any of claims 3 to 6, comprising a first set of at least one enclosing screw element (1, 4) and at least one enclosed screw element (3, 6), wherein the inner enclosed screw element (3) of the first set (1, 2, 3) comprises a cavity in which a second set (4, 5, 6) of elements is placed, said second set (4, 5, 6) comprising the same number of elements, and wherein said elements (4, 5, 6) of said second set, when given ordinal numbers, have profiles of a symmetry order which is equal to that of the profiles of the corresponding elements of the first set (1, 2,

3) having the same ordinal number.

10. The rotary screw machine of claim 9, further comprising at least one additional set of screw elements having the same symmetry order features as claimed in claim 9 for the first and second sets, said additional sets being placed in the interior of the second set or one in the interior of another additional set.

11. The rotary screw machine of claim 9 or 10, wherein screw elements (2, 5) of different sets of elements with profiles having the same symmetry order are rotatable about axes, the eccentricity of which is balanced when these elements are all taken together such that a statically and dynamically stable machine is obtained.

12. The rotary screw machine of claim 11, wherein each set comprises three elements, the middle element (2, 5; 2', 5 of which each being rotatable about an axis (O₂, O₅) which has eccentricity (E₂, E₅) with respect to a principal axis (X) about which the two other elements (1, 3, 4, 6;1', 3', 4', 6 of each set are centred.

13. The rotary screw machine of any of claims 9 to 12, wherein corresponding ones (3, 6; 1', 4'; 3', 60 of the screw elements in each set are driven into rotation, said driven elements being mechanically coupled.

14. The rotary screw machine of claim 13, wherein corresponding ones (2', 50 of the screw elements in each set which are not driven are mechanically coupled to each other.

15. The rotary screw machine of claim 12 or 13, wherein the driven elements (3, 6) are the inner elements of each set (1, 2, 3; 4, 5, 6), and wherein the outer elements (1, 4) of each set are not rotatable.

16. The rotary screw machine of claim 12 or 13, wherein the driven element (1', 40 are the outer elements of each set, and wherein the inner elements (4, 3', 60 are counter-rotated and coupled to the driven elements via an inverting mechanism (10).